Nitrate concentrations have increased in many Upper Floridian aquifer springs since the 1950s, exceeding 1 mg/L in recent years at some springs. The Upper Floridian aquifer is particularly vulnerable to impacts from anthropogenic activities in areas where the aquifer is not confined or only thinly confined, such as throughout much of Marion County, north-central Florida. Phelps (2004) reported that nitrate concentrations ranged from less than 0.02 to 12 mg/L, with a median of 1.2 mg/L, for 56 Upper Floridian aquifer wells sampled in Marion County during 2000-2001. Stormwater runoff is one of the possible sources of nitrate, among others suck as septic tanks, land-based application of reclaimed stormwater, or fertilizer, which can contribute to elevated nitrate concentrations in the Upper Floridian aquifer.
Wastewater and Sewage Treatment:
A problem arises when urban regions gradually expand due to regional development, centralized sewage collection, treatment, and disposal is often unavailable for both geographic and economic seasons. As a consequence, about a quarter of the residences in the United States relied on decentralized treatment of wastewater. As the stormwater runoff, household wastewater contains high concentrations of nutrients, primarily nitrogen and phosphorus, disease-causing organisms and viruses, and some toxic chemicals. Nationwide, wastewater effluent from on-site wastewater treatment (OWTS) can represent a large fraction of nutrient loads to groundwater aquifers: Phosphorus and nitrogen compounds are the most frequent measurements to indicate nutrient loadings. Some aquifers may discharge into springs or other surface waters adversely affecting public health. Hence, on-site wastewater effluent disposal has contributed significant adverse impacts to the dynamics of the natural environment.
Due to widespread septic tank failure, scientists, engineers, and manufacturers in the wastewater treatment industry have developed a wide range of alternative passive technologies designed to address increasing hydraulic loads, energy saving requirement, and water contamination by nutrients and pathogens in on-site wastewater treatment.
Onsite sewage contains organic matter (biochemical oxygen demand), suspended solids, nutrients, and some pathogens, which can cause a number of diseases through ingestion or physical contact. Those water-related diseases include shigellosis, salmonellosis, typhoid fever, and infectious hepatitis. More than 25 million homes, or 25 percent of the U.S. population, use onsite wastewater treatment systems to meet their wastewater treatment and disposal needs. The most common type of onsite wastewater treatment plant (“mini treatment plant”) is the septic system. When properly constructed and maintained, the septic systems can provide years of safe, reliable, cost-effective service.
A septic system consists of four main components. The first component is a home's indoor plumbing, which is a system of drains and pipes located inside a home in charge of transporting wastewater outside to the next major component, the septic tank. The septic tank is normally an underground, watertight container, made of concrete, fiberglass, or other durable material, which provides primary wastewater treatment. In the septic tank, solids settle to the bottom of the tank and partially decompose by naturally occurring bacteria resulting in a layer of soaps, greases and scum float on top of the liquid wastewater. There is a need to periodically remove the floating scum and submerged solids accumulated in the tank. The liquid wastewater between the floating and settled solids has to be discharged from the septic tank to the next major component of a septic system, the drainfield.
The standard drainfield that is constructed by a series of parallel, underground, perforated pipes allows the septic tank effluent to percolate into the surrounding soil in the vadose (unsaturated) zone where most of the residual nutrients may be assimilated. Through various physical, chemical, and biological processes, most bacteria, viruses and nutrients in wastewater are expected to be consumed as the wastewater passes through the soil. The type of effluent distribution in the standard drainfield systems include gravity systems, low pressure dosed systems, drip irrigation systems, etc. and some of them require having an additional pump.
Nutrients such as ammonia, nitrite, nitrate, and phosphorus are common contaminants in the water bodies all over the world, as well the emerging contaminants that affect aquatic ecosystems. All these nutrients have direct and indirect acute and chronic harmful outcome for human beings and ecosystems. Ammonia is an important compound in freshwater ecosystems. It can stimulate phytoplankton growth, exhibit toxicity to aquatic biota, and exert an oxygen demand in surface waters. Hence, primarily due to the limited nitrogen-removal treatment capabilities of conventional septic systems, their density of use in a watershed can produce adverse and undesired aquatic resource impact through accelerated eutrophication. Besides, unionized ammonia is very toxic for salmonid and non-salmonid fish species. Fish mortality, health and reproduction can be hampered by the presence of minute amount of ammonia-N.
Nitrate is more toxic than nitrite and can cause human health problems such as liver damage and even cancers. Nitrate can also bind with hemoglobin and create a situation of oxygen deficiency in an infant's body called methemoglobinemia. Nitrite, however, can react with amines chemically or enzymatically to form nitrosamines that are very strong carcinogens.
In addition, wastewater also carries different kinds of microorganisms such as bacteria like Escherichia coli and Salmonella typhi, protozoa like Cryptosporidium parvum and Giardia lamblia, helminthes and viruses like hepatitis A virus. Concentration of total coliform is about 107-109 no./100 mL, fecal coliform is about 104-106 no./100 mL, Cryptosporidium parvum oocysts is about 10-1-101 no./100 mL and Giardia lamblia cysts is about 10-1-102 no./100 mL in a medium strength wastewater. Oocysts and cysts are spore phase that will help certain microorganisms to survive for a long time. These entire microorganisms are responsible for different kinds of diseases like diarrhea, jaundice, food poisoning, dysentery and nausea. If these diseases are not controlled properly, they may cause harmful effect on health even death due to domestic sewerage pollution.
As a consequence, nutrient and pathogen removal is very important for the sustainability of the aquatic ecosystem and environment. There are many ways for homeowners with septic systems to minimize the potential nutrient impacts that on-site wastewater treatment (OWTS) may have on the environment. Yet early codes did not consider the complex interrelationships among nutrient impacts, soil conditions, wastewater characteristics, biological mechanisms and climate, or geoclimatic differences that might be big in vastly different regions.
At present, there is a need for promoting enhanced nitrogen removal in septic systems, as well as a better understanding of nitrogen removal behavior of the septic system effluent plume as it passes through soil to a receiving water body. In general, passive technologies might be advantageous due to their cost effectiveness, system reliability, and low maintenance requirement. This triggers an acute need to perform a thorough technology comparison, screening, and prioritization.
To reduce organic and nitrogen impacts, an aerobic treatment unit (ATU) may be used to treat wastewater prior to ground discharge, typically by adding aeration to promote decomposition of organic matter, reduce pathogens, and transform nutrients. Basic aerobic treatment unit designs include suspended growth systems, fixed-film systems, and integrated fixed film and suspended growth systems. All three types usually have a septic tank ahead of them that removes the large solids and provides some protection to the aerobic treatment unit. Yet passive treatment and disposal systems, which do not use aerator pumps and include no more than one effluent dosing pump, are relatively new (Chang et al., 2007). Passive on-site wastewater treatment is defined by the Florida Department of Health as a type of onsite sewage treatment and disposal system that excludes the use of aerator pumps and includes no more than one effluent dosing pump with mechanical and moving parts and uses a reactive media to assist in nitrogen removal. Reactive media are materials that effluent from a septic tank or pretreatment device passes through prior to reaching the groundwater. This may include but are not limited to soil, saw dust, zeolites, tire crumbs, vegetative removal, sulfur, spodosols, or other media. Hence, a new generation of performance-based, passive (as opposed to conventional) on-site wastewater treatment to effectively remove septic tank effluent nutrients and protect public health and the environment in a cost-effective manner will need to be devised and implemented with innovation.
For example, some technologies use a reactive media to assist in nitrogen removal. Saw dust and other wood products, zeolites, tire crumbs, vegetation, sulfur, spodosols, etc. have been suggested or used as such possible treatment media. These systems with new materials and methods will require increased focus on system performance, pollutant transport and fate, resulting environmental impacts, and an integration of the planning, design, sitting, installation, maintenance, and management functions. Cost effectiveness, system reliability, and proper management become the major concerns in applications. Treatment of Stormwater, Urban Runoff and Other Liquid Streams:
Another water management problem arises from stormwater runoff which is one of the possible sources of nitrate land-based application of reclaimed stormwater, or fertilizer, which can contribute to elevated nitrate concentrations in the Upper Floridian aquifer. Stormwater runoff is a known pollutant source capable of causing surface water degradation, especially in highly populated areas such as Central Florida. Wet detention ponds manage this stormwater, but most of the ponds do not remove enough nutrients, specifically nitrogen and phosphorus, to meet total maximum daily load regulations.
Most of the environmental management in the past few decades has focused largely on point-source pollution of industrial and municipal effluents. Not much comparable effort has been made to restrict the input of nitrogen and phosphorous from dispersed or nonpoint sources such as agricultural and urban runoff. As a result, anthropogenic inputs of nonpoint pollutants, particularly nitrogen and phosphorous, have increased dramatically. Elevated nutrient levels in surface and ground water may cause human health problems, such as blue baby syndrome, and may impair or destroy environmentally sensitive habitat through algal blooms and eutrophication.
Nitrogen-containing and phosphorous-containing compounds are found in urban stormwater runoff, primarily from highways. Nitrates normally result from vehicular exhaust on the roadway itself and are also contributed from fertilized landscaped areas and residential areas alongside the road. Considered one of the most efficient best management practices, a wet detention pond removes contaminants through physical, biological, and chemical processes. This practice is used to treat stormwater runoff before it enters a surface water body. According to Chapters 62-40 of the Florida Administration Code, a stormwater pond shall achieve an 80% average annual load reduction of pollutants from the influent stormwater. The current law refers to the removal of solids only. However, the pond can only remove a certain percentage of a contaminant, and the discharged pollution, although significantly less than in stormwater runoff, may still damage fragile ecosystems in the receiving water body. The data compiled by Harper and Baker (2007a) from previous research studies suggest that detention ponds do not achieve this 80% goal for the nutrient pollutants of concern. The averages of the removal efficiencies from these studies show a 37% removal of total nitrogen, 79% for orthophosphorus (OP), and 69% for total phosphorous. There is an acute need to provide innovative methods, systems, apparatus, and devices for nutrient control and management for sources of nitrogen and phosphorus including stormwater runoff.
The use of sorption media, such as compost, to capture pollutants from stormwater runoff started in the late 1990s. Stormwater infiltration systems were then widely used to address the quality issue of stormwater runoff through the use of either infiltration or exfiltration. Engineered soil mix that provides stormwater treatment through filtration has been deemed as a sustainable source-control option, and various types of applications have been promoted recently in the context of green infrastructure systems. Prior art discussed the simultaneous removal of nitrogen and solids in continuous upflow filters and a computer simulation of the nitrification process based on the Activated Sludge Model No. 1 developed by the International Association of Water Quality.
Many surface waters in Central Florida, such as Lake Jesup where nitrogen and phosphorus are considered the limiting nutrients for primary production, currently experience eutrophication problems caused by high nutrient loading from stormwater detention ponds (i.e., wet ponds). Stormwater runoff is just one possible source of nitrogen; others include septic tanks and land-based applications of reclaimed wastewater or fertilizer, which can elevate nutrient concentrations. In a total maximum daily load (TMDL) report for water quality improvement proposed by the Florida Department of Environmental Protection, the St. Johns River Water Management District examined several approaches to find a target nutrient concentration for Lake Jesup, which ranged from 0.04 to 0.08 mg/L for total phosphorus and 0.61 to 2.40 mg/L for total nitrogen. The St. Johns River Water Management District found concentrations of total nitrogen and total phosphorus that provide sufficient water clarity for growth of submerged aquatic vegetation over 25% of Lake Jesup.
Submerged aquatic vegetation growth should enhance fisheries and provide wildlife habitat, as well as reduce the resuspension of flocculent organic sediments. The total maximum daily load report for Lake Jesup also shows a current annual load entering the lake of 559,500 kg/year of total nitrogen and 36,000 kg/year of total phosphorus. Surface runoff accounts for 42% and 48% of the total nitrogen and total phosphorus loadings into the lake, respectively. To meet the total maximum daily load standards, the loading into the lake should decrease 52% for total nitrogen and 37% for total phosphorus. The total nitrogen and total phosphorus target concentrations that allow the 25% submerged aquatic vegetation criteria are 0.61 and 0.04 mg/L, respectively. These concentrations were used as the standards for Lake Jesup with regard to this research project. No point sources currently discharge into the lake, so these goals must result from reduced nutrient concentrations in stormwater runoff.
In addition to the applications of sorption media for wastewater treatment, our studies also evaluate the performance of a chamber upflow filter and skimmer in terms of water quality, water quantity, and overall operation and maintenance in association with stormwater wet ponds and runoff from pervious surfaces. Specifically, the objectives of this study include: (1) estimate the head loss through an upflow filter with a chosen media mix; (2) test the applicability of a surface skimmer; and (3) assess nitrogen and phosphorus concentrations leaving a detention pond using a chamber upflow filter and skimmer setup with a specific sorption media for pollution control.
Before 1995, much work was devoted to research for the removal of nutrients primarily with the sand filter method. For this reason, different types of sand filter methods had been developed like: 1) the Washington D.C. sand filter method, 2) the Delaware sand filter design and 3) the Austin sand filter. The removal efficiency of the Delaware sand filter is Total Suspended Solids (TSS) 70.20%, total phosphorus 71.10%, ammonia nitrogen (NH3-N) 67.00% and Total Kjeldahl nitrogen (TKN) 59.90%.
The use of upflow filtration for stormwater treatment is a relatively new idea to remove pollutants from contaminated stormwater runoff. Upflow filters have the advantage of longer run times and less maintenance than traditional downflow filters due to the design of the filter. Prior art used an upflow filter to treat runoff from highly contaminated critical source areas before it mixed with runoff from less contaminated areas. They studied a field application of the upflow filter inserted into a catch basin that achieved reductions of 70% for suspended solids, 65% for turbidity, and 18% for phosphorus. There are upflow filters commercialized for runoff treatment in stormwater inlets, and the successful integration of an upflow filter filled with the green sorption medium connected with a surface skimmer could provide a new best management practice to improve the quality of stormwater runoff.
Green sorption medium consists of several recycled and natural media that provide a favorable environment for pollutant removal to occur. Each type of medium assists in the removal of specific nutrients. Phosphorus sorbs to one type of medium, while another medium is utilized as a carbon source for nitrate removal under anoxic conditions. Anoxic environment has no free oxygen but does contain nitrate as electron acceptor for denitrification.
The combination of these elements provides a cost-effective treatment option to reduce nutrients traveling from wet detention ponds to surface waters. The present invention presents the use of a chamber upflow filter and skimmer (CUFS) filled with a specific green sorption medium as process modification of stormwater retention ponds, which can increase the removal of nitrogen and phosphorus in the stormwater runoff. A similar study had already proved the effectiveness of sorption medium for phosphorus removal from irrigation water in green roof chambers.
As a Statewide unified rule for stormwater management is being developed in Florida, there is a need to combine field and laboratory data for designing effective passive in-situ treatment units within stormwater retention/detention ponds for ultimate control of nitrogen impact on groundwater in Florida. The study leading to the present invention examined the ability of different sorption media to sorb nitrogen and phosphorus from stormwater contaminated with various fertilizers. Sorption media of interest include but are not limited to tire crumb, sawdust, activated carbon, iron amended resins, orange peel, peat, leaf compost, naturally occurring sands, zeolites, coconut husks, polymers, and soybean hulls. The study consisted of running both batch and packed bed column tests to determine the sorption capacity, the required sorption equilibration tire and the flow-through utilization efficiency of various sorption media under various contact times when exposed to stormwater contaminated with various nitrogen fertilizers.
Recent development shows that removal of ammonia, nitrite, nitrate, and phosphorus can be enhanced by mixing different sorption media, such as sawdust, tire crumb, sand, clay, zeolite, sulfur, and/or limestone, etc., with natural soil.
Appropriate media mix in this research is deemed as a kind of multifunctional material or functionalized sorption media that may be used in both natural and built environments to improve the existing physicochemical and microbiological processes for nutrient removal. Such media mix has the “green” implications because of the inclusion of some recycled materials, such as tire crumb and sawdust, as part of the recipe to promote the treatment efficiency and effectiveness. From engineering standpoint, with the aid of such green sorption media, nutrients in the water bodies can be reduced or even mostly removed by enhanced absorption/adsorption, nitrification/denitrification and other chemical reactions, such as precipitation and ion exchange.
The adsorption, absorption, ion exchange, and precipitation reactions are actually intertwined with physicochemical and microbiological processes in porous media intermittently. Pollutants removed by the adsorption process in the “green sorption media” may subsequently desorb. Two important biochemical transformation processes are the nitrification and denitrification that occur at the same time as the adsorption, absorption, ion exchange, and precipitation reactions move on. They result in the transformation of ammonia, nitrite, and nitrate via oxidation and reduction reactions in the microbiological process. In short, nitrification is a microbiologically mediated process that occurs under aerobic conditions, resulting in the formation of nitrate whereas denitrification is a microbiologically mediated process but occurs under anoxic or anaerobic conditions, resulting in the formation of gaseous forms of nitrogen. In reduction-oxidation chemistry, however, nitrification is a process in which ammonium is oxidized via nitrifiers and denitrification is a process in which nitrate is reduced to nitrogen gas via denitrifiers. However, nitrifiers can grow best in a temperature range of 350° C. to 420° C. and denitrifiers can work well in a range of 100° C. to 250° C.
The integrated impact of temperature changes on both physicochemical and microbiological processes remains unknown when removing nutrient in these sorption media mixes. Research resulting in the present invention was aimed at exploring how the filtration kinetics of selected filter media for nutrient removal is affected by various temperatures leading to improve the application potential of green sorption media in all weather conditions. It starts with a through literature review followed by the material characterization of a selected sorption media, and a laboratory column study that was conducted to simulate a wastewater/stormwater treatment unit with saturated media conditions. Such a filtration kinetics study led to a comparison to investigate the capabilities of comparing a natural soil with soil augmentations in regard to remove nitrogen and phosphorus associated with a range of initial nutrient concentrations at three different temperatures (i.e., 28° C., 23° C., and 10° C.).
On one hand, research and testing was aimed at an innovative design of the underground drainfield with soil amendments (sorption media) in a pilot septic tank system. The present invention includes the design of the underground drainfield with soil amendments (sorption media) in a pilot septic tank system. In the initial test runs, the new system located at the on-site wastewater treatment test center at UCF has been tested and proved cost-effective. The new system located at the on-site wastewater treatment test center, University of Central Florida, Orlando, Fla. was tested and proved cost effective in the initial test run.
High nitrogen and phosphorus concentrations in stormwater runoff, contaminated groundwater, landfill leachate, and domestic and industrial wastewater effluents have negatively impacted the drinking water quality in many regions. The use of filter media, such as tire crumb, sawdust, sand, clay, zeolite, sulfur, limestone, etc., to get better removal efficiencies of nutrients has been the focus in the planning and design of green infrastructure. These material mixes mainly promote the adsorption/absorption and precipitation of orthophosphate in physicochemical process and the transformation of ammonia, nitrite, and nitrate via oxidation and reduction reactions in the microbiological process. However, temperature changes affect nutrient removal efficiencies in both natural and engineered systems.
On the other hand, research and testing resulting in the present invention aimed to explore the filtration kinetics of selected filter media for nutrient removal at various temperatures to improve their application potential in all weather conditions. Constituents of concern include ammonia, nitrite, nitrate, total nitrogen, and orthophosphate. Such a kinetics study leads to investigate the capabilities of comparing a natural soil with soil augmentations in regard to removing nutrients under a range of initial concentrations at three different temperatures (i.e., 28° C., 23° C., and 10° C.). Significant differences of removal efficiencies associated with these prespecified temperatures were statistically confirmed by ANOVA analyses.
Greenroof Stormwater Treatment:
The most practical approach to the problem of stormwater runoff is to treat the stormwater as close to where it was contaminated as possible. The practice of using plant- and soil-based techniques for treating and holding stormwater at the source to decrease stormwater runoff and increase evapotranspiration rates is called low-impact development. A complete water budget on a non-irrigated green roof found that for small precipitation events, the green roof was able to retain approximately 75% of the precipitation and reduce the peak flow by as much as 90% as well as increase the time of concentration to almost four hours. The time of concentration is the amount of time it takes for stormwater runoff to occur after a precipitation event has begun.
Most of the environmental management in the past few decades has focused largely on point-source pollution of industrial and municipal effluents. Not much comparable effort has been made to restrict the input of nitrogen and phosphorous from dispersed or nonpoint sources such as agricultural and urban runoff. As a result, anthropogenic inputs of nonpoint pollutants, particularly nitrogen and phosphorous, have increased dramatically. Elevated nutrient levels in surface and ground water may cause human health problems, such as blue baby syndrome, and may impair or destroy environmentally sensitive habitat through algal blooms and eutrophication.